1. Field of the Invention
The present invention relates to a process for the measurement or checking of the geometric contours of a part without physical contact with the part, and to apparatus for carrying out the process.
2. Summary of the Prior Art
The majority of devices known for measuring or checking the geometric contours of a part operate by contact of a sensor with the part and measurement of the displacement of this sensor as a function of the displacement of the part perpendicularly to the sensing direction.
There are cases when this type of checking is not very suitable, for example when the contours to be checked are those of a distorted part, or when the checking rates must proceed evenly, or when the parts to be checked are very brittle.
This last instance is met, for example, in the checking of ceramic cores intended to act as moulding cores in the manufacture of hollow blades for aeronautical use. In the hot parts of turbojet engines (the high pressure turbine for example), blades are used which are cooled by a cooling fluid flowing through cavities of the blade. To make these blades at the foundry ceramic cores are made conforming to the shape of the inner cavities of the blades.
The geometric shape and size of these cores must be extremely uniform, with very little tolerance, as the form of the cores will determine the thickness of the walls of the cast blades and thus their ability to be suitably and evenly cooled. Individual checking is therefore indispensable. However, these cores are extremely fragile, it having been observed statistically that a pressure of 13 grammes exerted by a sensor is sufficient to break or distort them.